Shading coil motor assembly

ABSTRACT

A shading coil motor assembly including a pair of juxtaposed stator frames, each having a rotor, a common coil to produce magnetic flux for both stator frames, and drive shafts joined to the rotor on spaced, parallel axes for delivering torque to a common gear and output shaft.

United States Patent m1 Holper [451 Sept. 4, 1973 1 SHADING COIL MOTORASSEMBLY [75] Inventor: Frank Helper, Cary, Ill.

[73] Assignee: Molon Motor & Coil Corp., Rolling Meadows, Ill.

[22] Filed: Feb. 16, 1972 [21] Appl. No.: 226,787

[52] U.S. Cl 310/114, 310/172, 310/83 [51] Int. Cl. H02k 17/10 [58]Field of Search 310/162, 163, 40 MM, 310/172,83, 112,114, 90, 250,62,166; 74/409, 411

[56] References Cited UNITED STATES PATENTS 1,750,240 3/1930 Myer310/172 3,555,317 1/1971 Allan 310/62 3,543,064 11/1970 Holper 310/903,512,732 5/1970 Walsh i i 310/172 3,144,597 8/1964 Lee i i 310/1623,163,791 12/1964 Carlson 310/112 934,391 9/1909 Conradm. .1 310/1723,122,666 2/1964 Guiot 310/162 Primary ExaminerR. Skudy AttorneyJames B.Kinzer et a1.

[57] ABSTRACT A shading coil motor assembly including a pairofjuxtaposed stator frames, each having a rotor, a common coil toproduce magnetic flux for both stator frames. and drive shafts joined tothe rotor on spaced, parallel axes for delivering torque to a commongear and output shaft.

6 Claims, 4 Drawing Figures PAIENIEU 4975 .n 1.: rfEFrEEiFrmb FIG!SHADING COIL MOTOR ASSEMBLY This invention relates in general toelectric motors, and more particularly to a shading coil motor assemblyutilizing a double rotor-stator arrangement to drive a single outputshaft.

Small, single-phase induction motors of small fractional horsepower aresometimes started by means of a low-resistance, short-circuited singleloop of heavy copper wire, commonly called a Shading coil, which isplaced around one tip only of each pole, known as a shading pole. Thistype of motor is further characterized by a field or main windingconnected to the source of electric power and wrapped around an ironcore, corresponding to the primary coil or winding of a transformer.Each shading coil corresponds to a secondary transformer winding,short-circuited on itself. When the alternating current from the powersource, and therefore the field flux, are increasing, a portion of theflux cuts each shading coil. This establishes current in the shadingcoils, which sets up a flux in the related shading poles opposite themain field flux, and hence lines of magnetic force pass only through theunshaded sections of the poles.

The effect of the shading coils is to cause a flux t sweep across thepole faces, from the unshaded to the shaded pole sections. A weakrotating field is thus established, exerting a starting torque on therotor.

In Holper U. S. Pat. No. 3,543,064, a shading coil motor is constructedfrom two iron frames (laminated) arranged end-to-end in tandem relationwith the two air gaps aligned coaxially. A single coil is lapped aboutboth frames. Each frame houses a rotor, the two rotors being in coaxialalignment, and a comparatively long, common drive shaft is coupled tothe rotors. The drive shaft is equipped with a drive gear, driving apair of gears opposed thereto, and in turn the opposed gears are coupledto a common output gear.

The motor of the Holper patent, characterized by a single coil (copperwire) embracing two iron frames was devised in an attempt to maximizethe coil effect since one coil is cheaper than two; or in other wordsthe ratio of cooper:iron was reduced. Such a motor can be built todeliver as much as one-twentieth horsepower at the drive gear identifiedabove, a commendable achievement for a shading coil motor. Theconstruction, nonetheless, is expensive for while there is conservationin the copper cost, other costs are increased. Thus, the long driveshaft represents an appreciable unsupported length requiring a heaviershaft and heavy duty bearings in order to reduce shaft whip.Exceptionally long mounting pins are required to support the frames,making it difficult to comply with tolerance allowances. It is not amatter of a straight line increase in cost, but rather a geometrical orexponential increase. Briefly, there is a diproportionate cost when itcomes to shaft support and frame support.

In view of the foregoing the primary object of the present invention isto construct a shadingcoil motor capable of delivering as much asone-twentieth horsepower, incorporating the concept of a single coilservicing two frames, but with the frames so placed that the rotors areon parallel axes rather than on a common axis. With the rotors soplaced, compared to the arrangement of Holper US. Pat. No. 3,543,064,and in compliance with further objects of this invention, it is stillpossible to use a single coil and yet the drive shafts may be shorterwith less possibility of whip, the bearing supports need not be of aheavy duty type, the gearing is less strained, tolerances are moreeasily met, gear reduction may be easily varied. As to the latter, gearreduction in Holper US. Pat. No. 3,543,064 was limited between thecenters of the two gears and 66 thereof.

Other and further objects of the present invention will be apparent fromthe following description and claims and are illustrated in theaccompanying drawings which, by way of illustration, shows a preferredembodiment of the present invention and the principle thereof and what Inow consider to be the best mode in which I have contemplated applyingthat principle. Other embodiments of the invention embodying the same orequivalent principles may be used and structural changes may be made asdesired by those skilled in the art without departing from the presentinvention.

In the drawings:

FIG. 1 is a side elevational view of a motor assembly constructed inaccordance with the present invention;

FIG. 2 is an elevational view taken substantially along line 22 of FIG.1;

FIG. 3 is a schematic view of the present motor; and

FIG. 4 is a schematic view of a known motor.

The shading coil motor assembly of the present invention, generallyidentifiedby reference character 10, comprises a pair of juxtaposedmagnetic stator frames 11, a pair of rotors 12, one associated with eachstator frame, a pair of coil cores 13, one associated with each statorframe, a common coil 14 embracing both cores 13 to develop magnetic fluxin both stator frames, a single gear box 15 receiving the outputs ofboth rotors l2, and a common output shaft 16 extending from the gearbox.

Each stator frame 11 is U-shaped, FIG. 2, and includes a plurality ofstacked liaminations 20 in the fonn of iron plates. Shading coils 21,FIG. 2, are mounted on each frame 11. Rotor cavities 22 are formed ineach frame for receiving the rotors 12 which rotate freely therein. Therotors are in parallel spaced relation and extend through the cavitiesalong axes perpendicular to the laminations.

The cores 131 face each other and extend across and close the open endsof the U-shaped frames 11. The cores, like the frames, are defined bylaminations of an equal number as in the frames sothat the thicknessesare identical. The frames and cores are split to facilitate assembly ofthemotor. Since the frames are in side-byside relationship, the coresare in closely spaced parallel relation wherein their side faces l3a arein juxtaposed parallel spaced relation.

The coil 14 includes a conventional bobbin 25 formed of insulatingmaterial with a plurality of copper wire windings 26 thereon. Both thebobbin and the windings define a core opening 27 through which extendthe cores 13. Accordingly, it is seen that the single coil 14 commonlyembraces both cores 13 to produce flux for both stator frames whenenergized by a suitable potential, such as an alternating currentvoltage.

Each motor 12 is carried on a rotor shaft 30. Each shaft 30 is supportedat one end by a bearing assembly 31. The bearing assembly 31 is at themedial area of a yoke or plate 31?. The yoke is a die casting and isprovided at each end with spacers 31A.

Each shaft 30 is supported at the other end by a bearing assembly 32which extends from and is an integral part of the gear box 15. The gearbox is a die casting and includes spacers 115A opposed to the spacers311A. The frames are rigidly tied to the gear box by pins having boltheads 33 at one end and threads (not shown) at the other end fittingtapped openings in the spacers 15A.

The rotor shafts 30 extend outward of the bearing assemblies 31 and mayhave mounted on their adjacent ends fans 34 which are driven by therotor shafts to cause a flow of air across the stator frames 11 toenhance cooling of the motor assembly. 7 The rotor shafts 30 likewisecomprise inputs to the gear box 15 wherein the outputs of the rotors aretransmitted to the gear box and ultimately to the single common outputshaft 16. Drive gears 35 are secured to the rotor shafts l and inmeshing engagement with idler gears 36, the latter of which are suitablysupported by bearings within the gear box. The idler gears 36 in turnengage a common driven gear 37 which is mounted on the output shaft 16whereby power is transmitted from the rotor shafts through gears 35 and36 to gear 37 and the common output shaft 16. The sizes of the drivegears 35 and the idler gears 36 are identical, while the driven gear 37is substantially larger, thereby effecting a reduction in the gear trainbetween the rotor shafts and the output shaft.

Characteristic of a shading coil motor is a tendency to overheat. Forexample, a single rotor shading coil motor having a frame and coreassembly 2 inches thick with 310 turns of number 22 wire on the fieldcoil operating at 2.6 amps and 140 watts, will after 7 minutes ofrunning exceed an allowable 140C rise in temperature, the maximumpermitted under Underwriters Laboratories standards. However, the twinrotor shading coil motor assembly of the present invention with a singlefield coil of 300 turns of number 21 wire and twin 2- inch thick frameand core assemblies, will run continuously (with no fan) drawing 1.15amp and 77 watts, and sustain a temperature rise of only 982C withoutfans. There is more iron to radiate heat, but optionally, the fans 34may be used to enhance cooling if needed or desired.

A shading coil motor with a 2-inch thick iron frame and core assemblyhaving about 350 turns in the field coil will produce a starting torqueof 10 to 12 ounces, while coupling together a pair of stator frames witha single coil of only about 200 turns under the present invention willproduce about 18 ounces of starting torque which results in a 50 percentincrease with less copper. Again, the cooler motor is more efficient.Admittedly, there is a slight .increase in torque efficiency wherein twodrive pinions in a gear box necessarily and inherently impart a balanceddrive to the output shaft of the gear box but such a balanced drivearrangement accounts for at the most only 10 percent of the increasedtorque. The motor assembly of the present invention will develop aboutone-twentieth of a horsepower, which is not possible with a shading coilmotor of standard construction characterized by a single rotor andsingle frame arrangement. It should also be noted here that a capacitormotor with a gear box and rated equally to a motor constructed inaccordance with the present invention would cost at least twice as muchas the motor assembly of the present invention.

It will be appreciated that each rotor shaft delivers one-half theoutput, namely, about one-fortieth horsepower. The strain on the rotorshaft bearings is less than if there was one rotor shaft deliveringonetwentieth horsepower, to say nothing of the reduced cost factorsmentioned above represented by the fact that in motors of this kind thecost of bearings and shafts increases as the (torque or power)?Additionally, the gears 35 in delivering only one-fortieth horsepowerplace less strain on the gear train compared to the arrangement in thel-lolper patent where the rotor gear (gear 36) delivers one-fortiethhorsepower. This can be seen from FIGS. 3 and 4, approximately to scale,where FIG. 3 is a schematic view of the present motor and FIG. 4 is aschematic view of the motor of l-lolper U.S. Pat. No. 3,543,064. In FIG.4, B1 and B2 identify the bearing supports for the drive shaft couplingthe two coaxial rotors RT.

It will be understood that modifications and variations may be efi'ectedwithout departing from the scope of the novel concepts of the presentinvention, but it is understood that this application is to be limitedonly by the scope of the appended claims.

I claim:

l. A shading coil motor assembly comprising a pair of juxtaposedidentical magnetic stator frames, a rotor cavity in each frame, shadingcoil means on each frame, a rotor in each rotor cavity and each rotorhaving a rotor shaft, the rotational axes of said rotor shafts being injuxtaposed parallel spaced relation, a single common coil connected tosaid stator frames to develop magnetic flux simultaneously in bothstator frames when the coil is energized, and means for coupling therotor shafts to a single output shaft.

- 2. The combination as defined in claim I, wherein fans are coupled tothe rotor shafts for creating a flow of air across the stator frames.

3. The combination as defined in claim 1, wherein said coupling meansincludes a gear box.

4. A shading coil motor assembly comprising a pair of juxtaposedU-shaped magnetic stator frames, a rotor cavity in each frame, shadingcoil means on each frame at the cavity, a rotor freely rotatable in eachrotor cavity, each rotor having a rotor shaft the rotational axes ofsaid rotor shafts being in juxtaposed parallel spaced relation, the openends of the U-shaped frames facing each other and being closed bymagnetic coil cores, a common coil wrapped around said coil cores todevelop magnetic flux simultaneously in both coil cores when the coil isenergized, and means for coupling the rotor shafts to a single outputshaft.

5. A shading coil motor assembly as defined in claim 4, wherein saidcoupling means includes gearing means connecting the rotor shafts to theoutput shafts.

6. A shading motor assembly is defined in claim 5, wherein said rotorshafts extend from both ends of the rotors, and fans are mounted on oneend for cooling

1. A shading coil motor assembly comprising a pair of juxtaposedidentical magnetic stator frames, a rotor cavity in each frame, shadingcoil means on each frame, a rotor in each rotor cavity and each rotorhaving a rotor shaft, the rotational axes of said rotor shafts being injuxtaposed parallel spaced relation, a single common coil connected tosaid stator frames to develop magnetic flux simultaneously in bothstator frames when the coil is energized, and means for coupling therotor shafts to a single output shaft.
 2. The combination as defined inclaim 1, wherein fans are coupled to the rotor shafts for creating aflow of air across the stator frames.
 3. The combination as defined inclaim 1, wherein said coupling means includes a gear box.
 4. A shadingcoil motor assembly comprising a pair of juxtaposed U-shaped magneticstator frames, a rotor cavity in each frame, shading coil means on eachframe at the cavity, a rotor freely rotatable in each rotor cavity, eachrotor having a rotor shaft the rotational axes of said rotor shaftsbeing in juxtaposed parallel spaced relation, the open ends of theU-shaped frames facing each other and being closed by magnetic coilcores, a common coil wrapped around said coil cores to develop magneticflux simultaneously in both coil cores when the coil is energized, andmeans for coupling the rotor shafts to a single output shaft.
 5. Ashading coil motor assembly as defined in claim 4, wherein said couplingmeans includes gearing means connecting the rotor shafts to the outputshafts.
 6. A shading motor assembly is defined in claim 5, wherein saidrotor shafts extend from both ends of the rotors, and fans are mountedon one end for cooling purposes.